Culture-dependent and -independent molecular analysis of the bacterial community within uranium ore

The bacterial community structure within a uranium ore was investigated using culture-dependent and -independent clone library analysis and denaturing gradient gel electrophoresis of 16S rRNA genes. The major aerobic heterotrophic bacteria were isolated and identified, and their resistance to uranium and other heavy metals was characterized. Together with near neutral pH, moderate organic carbon content, elevated U and other heavy metals (V, Ni, Mn, Cu, etc.), the ore showed high microbial counts and phylotype richness. The bacterial community mainly consisted of uncultured Proteobacteria, with the predominance of γ - over β - and α -subdivisions, along with Actinobacteria and Firmicutes. A phylogenetic study revealed that nearly one-third of the community was affiliated to as yet uncultured and unidentified bacteria having a closer relationship to Pseudomonas. Lineages of Burkholderiaceae and Moraxellaceae were relatively more abundant in the total community, while genera affiliated to Xanthomonadaceae and Microbacteriaceae and Exiguobacterium were detected in the culturable fraction. More than 50% of the bacterial isolates affiliated to Stenotrophomonas, Microbacterium, Acinetobacter, Pseudomonas and Enterobacter showed resistance to uranium and other heavy metals. The study showed for the first time that uranium ore harbors major bacterial groups related to organisms having a wide range of environmentally significant functional attributes, and the most abundant members are possibly new groups/taxa. These findings provide new insights into U-ore geomicrobiology that could be useful in biohydrometallurgy and bioremediation applications.